Silence! The Last of the Giant Radio Telescopes Is Listening to the Universe

There’s a geek mecca in them thar hills. And don’t expect your iPhone’s GPS to guide you to it. Hidden in the green hills of West Virginia, in a 13,000-square-mile National Radio Quiet Zone, is the world’s largest fully steerable telescope.

The GBT (Great Big Telescope, Great Big Thing or Robert C. Byrd Green Bank Telescope, depending on whom you ask) is the most overbooked telescope in the world. The waiting list to get some time on this baby is long and prestigious. And with good cause: Its sensitivity to radio signals is unparalleled.

The telescope is so sensitive, in fact, that the National Radio Astronomy Observatory (NRAO) has a van that drives around the surrounding countryside asking people to stop using their wireless speaker systems, electric fences, broadband wireless modems, military radar, etc. — anything that might interfere with the telescope’s readings.

With the growing popularity of radio-array telescopes, the GBT may end up being the last single-dish telescope of its kind built in the world. The difference between an array and a giant single-dish like the GBT is the difference between a zoom and wide-angle lens on your camera. The GBT is extremely good at finding a source in space by searching a wide area, while the radio array is like a telephoto lens that good at looking at the details.

Read on for a tour of this towering instrument of space exploration.

Above: The GBT is 485 feet tall, a nudge taller than the Statue of Liberty and a nudge shorter than the Washington monument. It was put into service in early 2000.

Below: The NRAO’s 140 telescope is just around the corner from the GBT. The 140 was out of service for a number of years, but has been brought back online in conjunction with an MIT project to study turbulent properties of the earth’s ionosphere.

The 16-million-pound Great Big Telescope cost $75 million to build, but some would say it has already paid back the investment. The GBT is helping prove Einstein’s general theory of relativity by discovering the high masses and short rotation periods of pulsars.

The GBT Feed Arm (above, top right) is where all the radiation from the dish is reflected before being redirected to the receiver room. It’s offset from the center of the dish, so it doesn’t obscure any portion of the sky.

The only vehicles permitted on the NRAO property are diesels, from ancient pickup trucks and vintage Volkswagens to more-modern diesel autos. Unlike gas-guzzling vehicles, diesels don’t use spark plugs for ignition, the sparks from which would interfere with the telescope’s readings.

The GBT’s time is split into about one-third pulsar research, one-third astrochemical research and the rest a hodgepodge of mapping projects, including hydrogen clouds and various radar signals. The objective is to receive, detect and amplify.

The surface of the GBT is made up of 2,004 individual panels, each of which can be adjusted to an accuracy of 0.3 millimeters.

“Everything is one of a kind, and we are constantly pushing the technology,” says Bob Anderson, who obviously loves his job. Living this far out in the hills of West Virginia has been an adjustment for his wife, but she has adapted and has been honing her online shopping skills.

Walking on the surface of the GBT must be something like walking on the moon. Even as you make your way along the surface, it is almost impossible to grasp the overall size of the dish, and the shiny white surface makes it difficult to orient yourself.

Although the GBT can only run one receiver at a time, eight are mounted on this rotating turret above the receiver room. You can see a couple of the larger receiving horns with heat ducts pointing at their tops. It can get mighty snowy and cold in this part of the world, which makes keeping the radio operating a challenge.

The hardware for the eight receivers is shown from below. The room is filled with a loud racket from the helium pumps that keep the instrument in a temperature window between 10 and 50 Kelvins (442 to 370 degrees below zero Fahrenheit). The different receivers are used to detect radio frequencies, ranging anywhere from 1 gigahertz up to 90 gigahertz.

Bob Simon, an Electronic Engineer at the NRAO, holds the new feed horn for a 7-pixel focal-plane array. They are hoping to implement the new radio receiver this winter for ammonia mapping in the K band, between 18 and 26 megahertz. The humid West Virginia summers make it almost impossible to read the K band, as any moisture in the air blocks the signal, highlighting the minute nature of the information the GBT detects and the sensitivity of the instruments it uses.

Justin Buzzard, a painter working for the NRAO, climbs out of his painting rig.

“I love this thing,” said Scott Gordon, who was helping inspect the telescope. “It is definitely an optical illusion. You realize how high up you are when you have a 60-foot rope and it’s not touching the ground.”

The GBT whirls itself around full-circle in nine minutes on four sets of four-wheeled trucks. The wheels carry more than a million pounds each. The original track had a number of design flaws which made it buckle. Fixing it cost millions of dollars, but now the telescope rotates smoothly.

The control room is so far away, a small plane could land between it and the GBT. In fact, the intervening fields do have an old airstrip. The control room has some rather dated computers lying about, but we were assured they have plenty of computing power to get the job done.

The entire control room is a Faraday cage, as in the movie “Enemy of the State” with Gene Hackman. The Faraday cage is used to keep the computer noise in and any radio-frequency interference out. The operators can look through windows covered with wire mesh to the GBT a couple of miles away.

Like a giant dinosaur roaming the Earth, the GBT makes a profound impression on the landscape. The telescope can reach full elevation in four minutes on a shaft just 30 inches in diameter, which was specially designed to handle the 16-million-pound load. Its size is in fitting proportion to the tasks that it undertakes, probing incomprehensible distances and documenting alien planetary phenomena.

Update: This story has been corrected with the proper weight for the GBT.

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